1. Field of the Invention
The present invention relates to a mobile communication system including an outdoor public base station, an indoor private host phone unit, and a mobile station formed by a cordless handy phone unit, and more particularly, to an improvement of a simultaneous incoming call receiving operation when the mobile station is located within an area where a service area of the base station overlaps a service area of the host phone unit.
2. Description of the Related Art
With a so-called second generation cordless telephone system including an outdoor public base station connected to a fixed network, an indoor private host phone unit (base station) and mobile stations, there are calls made basically outdoors by way of the base station (hereinafter referred to as outdoor public calls), those made basically indoors by way of the host phone unit (hereinafter referred to as indoor private calls) and those made from mobile stations to others by directly transmitting and receiving radio waves without using the base station and the host phone unit (hereinafter referred to as inter-mobile station direct calls).
When one of the mobile stations is waiting for an incoming call, it acquires the broadcasting information including channel structure information being transmitted from the base station or the host phone unit and operates intermittently for reception (hereinafter referred to as intermittent receiving operation) in accordance with the transmission timing of the paging calling channel it obtained by using the broadcasting information.
In a synchronous incoming call waiting (receiving) mode for the base station and the host phone unit, however, since the reception timing of the mobile station is formed by combining intermittent reception timings of the base station and the host phone unit, the number of receptions and the number of times of switching reception frequencies will becomes enormous which will increase the power dissipation of the mobile station. As a result, the operation hours of the mobile station that is generally powered by batteries is inevitably made very short. This will be explained later in detail.
If it is able to wait for a plurality of calls including outdoor public calls, indoor private calls or inter-mobile station calls, the mobile station waits for incoming calls sequentially on a time-sharing basis if necessary. For example, JP-A-7-143557 discloses a cordless telephone system adapted for waiting for incoming calls sequentially on a time-sharing basis particularly for outdoor public calls and inter-mobile station direct calls, and JP-A-7-147695 discloses a cordless telephone system adapted for waiting for incoming calls sequentially on a time-sharing basis particularly for indoor private calls and inter-mobile station direct calls.